The action of Game of Thrones didn’t really pick up until poor Ned lost his head, and the same could be true of House of the Dragons and the death of King Viserys.
Stannis Baratheon didn’t debut until the beginning of Season 2; could the same happen with Aegon, who was simply not present at the Red Keep during House of the Dragon Season 1?
I’ve actually suspected ever since Paddy Considine was announced as Viserys that House of the Dragon would follow a similar format to Game of Thrones as far as the lead character’s longevity is concerned.
Now, the fact that Paddy Considine has been cast as King Viserys, Alicent’s status as Viserys’ wife isn’t confirmed, and there is no mention of Aegon suggests that House of the Dragon at least starts with some time to spare before the Dance of the Dragons kicks off.